Re: [Discuss-gnuradio] Can threading disturb sensing continuety

[Brian Padalino]

On Fri, Mar 20, 2009 at 9:34 AM, kaleem ahmad <address@hidden> wrote:
>
> Thanks Ed,
>
> ADC sampling rate = 64MHz
> it gives resulution time = 1/64MHz = 156 ns
> if we choose N=512 for FFT then total observation time for one scan(one
> complete FFT) is = 156ns x 512 = 8 micro sec
> if the maximum possible (expected) cycle time is 200ms then:
> it needs 200ms/8microsec = 2500 continues FFT scans to cover the range of
> frequencies that correspond to 200ms cycle time.
>
> Is above calculation correct?
>
> The other possibility to increase the observation time is to increase the
> FFT size, but to cover entire 200ms would need 200ms/1/64MHz = 12800000 =
> FFT size (Which is not possible! Is it ???)
>
> Now please comment if my above calculations are correct or not and secondaly
> if my calculations are correct then how can I process (using GNURadio) 2500
> cosective FFT's (with surety that no FFT in between these 2500 FFT's is
> missing due to slow processing or thread switching) to find two peaks in a
> single array (availability of two peaks will give me the oppertunity to
> calculate the time distance between them).

It sounds like you're trying to do autobaud for an unknown FSK system
- but using the frequency domain to do this instead of the time domain
phases.

I'd recommend thinking of an algorithm in the time domain that would
suit your needs.

Brian